Asked by brad

The second term in a geometric sequence is 20. The fourth term in the same sequence is 45/4, or 11.25. What is the common ratio in the sequence?

Thanks for reading :)
Answered by brad (again)
Forgot to mention that I'd really appreciate an explanation not just a bare answer.
Answered by oobleck
The second term in a geometric sequence is 20 ... ar = 20
The fourth term 45/4 ... ar^3 = 45/4
Now divide:
ar^3 / ar = (45/4) / 20
r^2 = 45/80 = 9/16
r = ±3/4
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